When someone else is talking. Quietness is key. When someone else is painting a picture of how they see the world. Give them space. Be quick to listen - not to speak. 

Yes you have knowledge. Yes you have seen this stuff before. Yes you have some of the answers. 

No one actually cares when telling their story. They will care later when it matters - for now listen - ask questions - get a fuller picture - be curious.

THEN you will have more information (probably still not enough) to test if your knowledge, experience and 'at the ready' answers are right for this imperfectly unique situation.